I know this thread is a little old, but if anyone bypasses the output stage, the 1uF phono section caps look symmetrically mounted, but are not! That's why I only had output on one channel. Doh!
Actually, the output stage is the problem with this pre-amp. I concluded in the end that it was colouring the sound too much and would take too much to mod so I replaced my Yaqin with something more suitable. These are difficult to access and work on. The phono pre part is actually very good.
For the person who used 6N1P for the ECC83 / 12AX7 you should try a 6N2P as this has more gain which is needed in the first stages and will be more correctly biased with the fitted components as it is close to the 12AX7.
6N1P or 6N23P would be good in the output stage but would entail changing the heater wiring and the bias. Same goes for an ECC88 or 6DJ8.
Paul.
For the person who used 6N1P for the ECC83 / 12AX7 you should try a 6N2P as this has more gain which is needed in the first stages and will be more correctly biased with the fitted components as it is close to the 12AX7.
6N1P or 6N23P would be good in the output stage but would entail changing the heater wiring and the bias. Same goes for an ECC88 or 6DJ8.
Paul.
I changed my 1uF output bypass caps and didn't have any issues with a dead channel. Currently not running this pre tho. My re-built Citation 17 sounds better with my CDs and a DIY pono preamp.
Cheers,
Bob
Everyone that owns this Yaqin should take a look at the Volume pot. Mine went bad and killed a channel. There is no sense in upgrading the Caps if you got it going thru a 2 dollar volume pot.
How to rewire for 6V heater tubes
can you please let me know how to do this? did you run the 2 tubes in series off one supply?
any pix of the mod?
Thanks
can you please let me know how to do this? did you run the 2 tubes in series off one supply?
any pix of the mod?
Thanks
heater wiring
I have ms 12b and like to mod like others...
you mean i need to add one more transformer?
I have ms 12b and like to mod like others...
you mean i need to add one more transformer?
Hi!
I have owned the MS-12B pre a couple of years now. A friend with electronic skillz recommended it.
So, purchased it, and he helped me do the mods.
He told me to get JJ ECC82/ECC83(I think).
And he replaced the two caps that looked like this:
With a matched pair of this russian NOS paper-in-oil caps:
It really changed the sound from average to outstanding! It sounds very expencive, but is not.
About the pot, is it a dual 100kOhm? I got a blue alps like that and if it is a match it will go in there.
I have owned the MS-12B pre a couple of years now. A friend with electronic skillz recommended it.
So, purchased it, and he helped me do the mods.
He told me to get JJ ECC82/ECC83(I think).
And he replaced the two caps that looked like this:
With a matched pair of this russian NOS paper-in-oil caps:
It really changed the sound from average to outstanding! It sounds very expencive, but is not.
About the pot, is it a dual 100kOhm? I got a blue alps like that and if it is a match it will go in there.
Resistor
Still need to know if I can replace that 15 ohm 7 watt with a 22 ohm 5 watt? Thanks for the other info though.
Still need to know if I can replace that 15 ohm 7 watt with a 22 ohm 5 watt? Thanks for the other info though.
If no-one else will help, try this; Ohm's Law Calculations With Power
If I have it right, you want to drop 10 volts, as the heater transformer is 16v, x 1.4 rectified and smoothed, =22v. 22-10=12v. Using the calculator, I get 4.5w dissipation, which is pushing it a bit for a 5w resistor. As I use a 20R resistor to get 12v (22R gave me 11v), that dissipates 5w, so I got a 10w resistor here- eBay - The UK's Online Marketplace. He doesn't seem to have any more at the moment, but I have a spare if you need it. Why do you want to use a 5w? 10w WILL fit, only just.
Hopefully someone more expert will help, but that is the best I can offer.
By the way, removing or bypassing the volume control, output board, relays improved things. I also removed the 2 push button switches and put in a pair of WBT RCA sockets instead (I already had them), so the phono inputs are on top. Replaced the RIAA resistors with Takman metal films, and the caps with Russian teflons. Changed the input loading resistors to 1megs (for my Decca) and then paralleled them to get what I want. DIL single pin sockets to make them plug and play. Outputs from RIAA section or normal output via different sockets. At the moment it sounds better going through both sections, but I have TVC preamp, so YMMV.
This is a absolutely fantastic Phono/preamp if you are starting to get into tubes. I can't recommend it enough. I've added a better Volume pot, I have 1 UF sonicap gen 1 bypassed with sonicaps gen 2 .01 UF caps. I've added bradley allen gridstoppers. I have caddock's 47K resistors. I've also added some bypass caps in the powersupply. For the price, its unbeatable. This preamp has given me more joy than the $1200 Cornet 2 I have. I have to double check everything and put up the Yaqin for sale. All its doing is collecting dust.
Here is the insides: And yes, those are Blackgates capacitors in there.
The UnderBelly: you can see the Bypass Caps, 47k resistors, Gridstoppers
The UnderBelly: you can see the Bypass Caps, 47k resistors, Gridstoppers
Have I read that right? Why is the Yaqin for sale if it has " has given me more joy than the $1200 Cornet 2"?. This preamp has given me more joy than the $1200 Cornet 2 I have. I have to double check everything and put up the Yaqin for sale. All its doing is collecting dust.
Also, is the 4 pin connector from the tranny original, or did you fit it? And my unit is a 240v model so 20R is better for the 5814 (ECC82) heaters.
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